How 3- to 8-cu. yd. wheel loaders settled into a period of refinement

Two types of transmissions are commonly found on wheel loaders: hydrostatic and torque converter. With torque converters, the lock-up feature is standard on some models and optional on others. “Hydrostatic is simpler and has fewer moving parts,” says Mike Stark, product specialist, heavy wheel loaders with Doosan. “Another benefit of hydrostatic is better power management and, with that, better fuel economy.

But, hydrostatic transmissions generate more heat than torque converter transmissions at higher speeds and in demanding applications. Hydrostatic is generally better in short run applications, while torque converters work better for longer runs. Both hydrostatic and torque converter are well-established technologies, familiar to both operators and service personnel.”

Torque converter transmissions usually have four or five speeds. Often the 4-speed version is standard and the 5-speed optional. Case loaders in this range come standard with a 4-speed transmission; the 721F, 821F and 921F are available with an optional 5-speed unit with lock-up and computer-controlled clutch modulation. “Applications with a lot of roading, including municipalities, agriculture and quarries benefit from the efficiencies of a 5-speed transmission,” says Brad Stemper, solutions marketing manager, Case Construction Equipment. “And the lock-up torque converter gives the operator more gear selections to keep the engine in its best power range, increasing fuel savings at roading speeds and improving acceleration and hill climbing.” The 5-speed also has the Case Powerinch feature, which improves accuracy and control in tight loading applications. The 4-speed transmission has a lower initial cost and is a good choice for customers whose applications won’t take advantage of the features offered by a 5-speed setup.

But even when transmission type is matched to a machine by duty cycle and other considerations, further refinement is often needed because of the variation in demand of different types of loading.

Modes match performance to applications. The fully automatic, electronically controlled ZF AS Tronic transmissions in Hyundai loaders have three modes, for example. Automatic Light (AL) is for traveling longer distances at higher speeds. Automatic Normal (AN) is for mixed applications that involve both short travel distances and occasional longer travel. Automatic Heavy (AH) is for use in constrained environments, such as all-day V- or L-pattern loading.

“With multiple modes, a self-adjusting clutch and self-diagnostic capabilities, these transmissions provide maximum productivity while controlling owning and operating costs,” says Corey Rogers, marketing manager, Hyundai Construction Equipment Americas.

Operators of Caterpillar loaders can choose from three modes that shape overall machine response. Hystat mode provides aggressive engine braking and enhances productivity in loading operations. Torque converter mode allows freewheeling on descents and around corners, reducing both operator fatigue and fuel use. Ice mode enhances traction in slippery underfoot conditions. “Our 926M, 930M, and 938M small wheel loaders all have this Powertrain Mode selection, since it’s part of the Caterpillar Intelligent Hydrostatic powertrain system,” says Joel Grimes, small wheel loader marketing engineer.